Supervisory control and telemetering system



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Aug. 17, 1943'. w. A. DERR 2,327,251-

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Aug. 17, 1943.

SUPERVISORY CONTROL AND TELEMETERING SYSTEMS Filed July 29, 1941 4 She ets-Sheet 3 lamps Si k .M

770/75 m/ffer WITNESSES: r' 5247% 96a a/ Aug. 17, 1943. i R 2,327,251

SUPERVISORY CONTROL AND TELEMETERING SYSTEMS Filed July 29', 1941 4 Sheets-Sheet 4 INVENTOR M/Mrdflfierr.

ATTORN Patented Aug. 17, 1943 SUPERVISORY CONTROL AND TELEDIETER- ING SYSTEM Willard A. Derr, Wilkinsburg, Pa., assignor-to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania 8 Claims.

My invention relates, generally, to supervisory control and remote metering systems and,

more particularly, to systems for performing both supervisory and telemetering functions over a single communication channel.

Heretofore telemetering and supervisory control functions have had to be performed utilizing separate communication channels when the channels were carrier current channels.

An object of my invention is to provide a combined supervisory control and remote metering system which shall function to perform both supervisory control and telemetering operations over a single carrier current communication channel.

Another object of the invention is to provide a combined supervisory control and impulse type remote metering system which shall function to perform impulse selective control and supervisory operations and impulse type telemetering operations employing a single communication channel.

A further object of the invention is to provide an impulse type remote metering system which shall function to so modify and cooperate with previously known selective control systems having a single communication channel as to provide remote selective supervision and control and remote impulse type metering.

These and other objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, the four figures of which, when interconnected as indicated, comprise a diagrammatic view of a combined selective supervisory control and remote metering system embodying the principal features of my invention.

The preferred embodiment of the invention is shown and described herein as it is applied to the supervisory control system of the H. P. Boswau Patent No. 2,208,535, issued July 16, 1940, most of the elements of the system of the Boswau patent being shown in the same cooperative relation herein as in the Boswau patent and the elements bearing the same reference characters as in the Boswau patent drawings. Certain relays, conductors and other elements of structure have been omitted and others added, and certain relay contact elements have been added to and others omitted from the relays of the Boswau patent. The added elements are designated by reference characters not found in the Boswau patent and the added and altered parts of the system are shown in heavier lines Application July 29, 1941, Serial No. 404,452

in the drawings so that the invention may be more readil understood.

For convenience of description, to avoid needless repetition, and in order that the invention may be more clearly set forth and understood, reference will be made in this specification to the Boswau Patent No. 2,208,535 for the description of elements and combinations of elements and their functioning that ai'hoffiihon tiff the two systems and which are fully described in the Boswau patent,

Considering the general aspects of the invention, the system disclosed and described in the Boswau Patent 2,208,535 has been altered by causing it to operate over a carrier current channel in order to show how the invention will function to perform both supervisory control and telemetering operations over a single carrier current signaling channel.

The conductors 2!!! and 223 are conductors of a power system extending between a control and a remote station. Carrier current impulse sending and receiving devices 502 and 102 at the control and. remote stations respectively function to transmit carrier current impulses over the conductors 2l9 and 223' in response to the actuation of the sending relays 20l and 4M respectively by the supervisory control system, and to respond to carrier current impulses transmitted over the conductors 2H) and 223 for supervisory control to actuate the line relays 200 and 400. The sending relays Zill and MN and the line relays 20D and 400 thus function in a manner similar to the corresponding relays of the system of the Boswau patent referred to hereinbefore.

A telemetering transmitter, which may be similar to that described in the patent to Lenehan No. 2,137,090, issued November 15, 1938, actuates a contact element 704 at the remote station to cause the carrier current device 102 to send-impulses at a frequency proportionate to the quantity measured at the remote station and which is to be indicated at the control station. At the control station an impulse receiver is connected to be actuated by the carrier current responsive device 502 in response to impulses transmitted from the remote station and to actuate an indicator to indicate the quantity measured at the remote station.

Considering the principal aspects of the invention more in detail, the carrier current device 502 at the control station comprises capacitive coupling devices 504 and 596 associated with the power lines 2!!! and 223 and connected in circuit with the high potential winding of a high frequency transformer 535. One low potential winding of the transformer 588 is connected to be energized by an oscillator which functions to generate high frequency currents when its energizing circuit is closed by a contact element 5H] of the sending relay 26!. Another low potential winding of the carrier current device 502 is connected to energize a relay 5i2 whose contact ele-- ment SM is connected in an energizing circuit for the line relay 286.

At the remote station the carrier current device 702 is similar to the carrier current device 502 and comprises a transformer I68 with its high potential winding connected to capacitive coupling devices 58 i and H36, a low potential winding connected to be energized by an oscillator, and another low potential winding connected to energize a relay H2. The oscillator may be controlled to generate impulses by the contact element 703 of the telemetering transmitter or by the contact element H of the sending relay AOL The contact element H4 of the relay H2 is connected in the energizing circuit; of the line relay 400.

Since the carrier current system is one in which there is no actual connection for current flow between the sending relays 2B! and dill and their associated receiving er line relays 550 and-60,

the system of the Boswau patent has been a changed from a closed circuit system, characterized by means for causing the line relay 200 and 408 to be normally energized and operated on each pulse by deenergizing and then reenergizing the relays, to an open circuit system characterized by a normal deenergized condition of the line relays 299 and 400 and operating the line relays by energization and subsequent deenergization on each pulse. Thus when the relays 2% and 400 are connected to negative potential they are pulsed by the relays EH2 and H2 whose contact elements 5M and H 3 connect their associated relays 285 and 408, respectively, to positive potential. The connections to the contact elements of the line relays 26B and 508 have been reversed so that an impulse comprising energization and deenergization of the line relays 280 and 400 will hav the same effect on the supervisory control system as an impulse comprising deenergization and reenergization has on the closed circuit system of the Boswau patent. Thus a control impulse will cause the line relay 200 to break the circuit of the reset relay 202 by energizing the line relay 290 whereas a control impulse will cause the line relay 200 of the Boswau patent to break the circuit of the reset relay 262 by deenergizing the line relay 260.

At the control station the point selecting relay I34 functions by means of its contact element 5H5 to connect the impulse receiver to be energized by the relay 5l2. The point selecting relay 310 at the remote station functions through its contact element H8 to connect the contact element 103 of the telemetering transmitter to control the oscillator of the carrier current device H12.

A pendulum relay 5H! and an auxiliary relay 520 at the control station function in response to the operation of a telemetering reset key 522 to reset the supervisory control apparatus at the control station by applying an impulse to the system of much longer duration than the supervisory control coding impulses and the telemetering impulses. A pendulum relay '1 I 8 and an auxiliary relay 120 at the remote station function in response to the long reset impulse to reset the supervisory control apparatus at the remote station. The pendulum relays EH8 and H8 comprise contact making armatures 5I9 and 119 which, when released by deenergization of the pendulum relays, oscillate to alternately make and break the circuit of their associated time delayed release relay 520 and (20, respectively. The relays 520 and 128 are so timed as to hold in durin the interval between break and make of their circuits by the armature 549 and H9 and they drop out a short time after the contact armatures 5H) and H9 stop oscillating. The time interval of oscillation of the contact armatures of the pendulum relays 518 and 718 may be several seconds so that they will not cause the release of the relays 528 and 120 when affected by supervisory control or telemetering pulses.

An auxiliary relay 122 at the remote station functions in response to the contact elements 124 and 126 of the relays 403 and 4i 1, respectively, to remove negative potential from the line relay 400. A contact element 128 of the relay 120 also functions to remove negative potential from the line'relay 550.

In the operation of the system, when it is desired to obtain an indication at the control station of a measured quantity at the remote station, the point operating key...i, l .24 is operated momentarilf to complete a shunting circuit for the winding of the starting relay l3l, and the deenergization of the starting relay 131 will cause the supervisory control apparatus at the control station to energize the pulsing relay 2D! with a code which is associated with the control point No. 4 with which point relay I35 is associated, as fully explained in the hereinbefore referred to Boswau patent. The coded pulsing of the sending relay 20! at the control station will cause it to close its contact element 510 to control the oscillator in a circuit which includes the conductors 524 and 526. The oscillator may be any suitable high frequency oscillator which will generate a high frequency potential so long as its circuit is closed. A low potential winding oi the transformer 568 is connected to be energized by the oscillator and high potential impulses will be induced in the secondary winding of the transformer 538. The capacitive coupling of the transmission line conductors 2l9 and 223' with the high potential winding of the transformer 508 through the condensers 5M and 505 will cause the high frequency coded impulses to be transmitted over the transmission line conductors 2 l 9 and 223 where they will act upon the high potential winding of a corresponding carrier current transformer through condensers hi4 and 706. The receiver relay H2 at the remote station will be affected by the coded impulses, and will actuate-its contact armature ll-l to energize the line relay 490 in accordance with the coded impulses in a circuit which extends from positive potential through the contact element I IA of the relay H2 in its operated position, a conductor 129, the winding of the line relay 490, conductors and 132, and a contact element 134 of the relay I22 in released position to negative poten tial.

The coded impulses acting upon the relay 400 will cause the supervisory control apparatus at the remote station to select and operate the point relay 3) which is associated with point No. 4 at the remote station, as fully described in the Boswau patent hereinbefore referred to. The point relay 3l0 will close its own holding circuit through one of its contact elements and the contact element 431 of the relay 412 as explained in the Boswau patent.

The operation of the point relay SIG at the remote station will cause the supervisory control apparatus at the remote station to intermittently energize the relay 40 I, whose contact element 1 l will intermittently close the oscillator circuit comprising a conductor 136, a conductor "I38, contact element 1H) and a conductor M0. The oscillator at the remote station will operate through its carrier current transmitting apparatus to transmit to the control station coded impulses associated with the point No. 4 with which the point relay I34 at the control station is associated.

When the coded impulses have been transmitted from the remote station to the control station, the relay 4H at the remote station will be energized, the relay 403 at the remote station will be deenergized, and the contact element 126 and T24 of these relays will complete an energizing circuit for the relay 122 which extends from positive potential through the contact element 728 of the relay M l, a conductor M2, the contact element 124 of the relay 403, a conductor hid, the winding of the relay 122, a conductor M6 and a contact element 148 of the point relay Bill to negative potential; The actuation of=the relay I22 will remove negative return potential from the line relay 409 and prevent it from being operated by impulses received by the receiving relay H2.

The operation of the point relay 3H] at the remote station functions to connect the contact element 103 of the telemetering transmitter at the remote station in a control circuit for the oscillator which extends from one terminal of the contact element 163, through a conductor I58, the contact element H6 of the point relay 3E6, the conductor 138 through the oscillator, the conductors 74D and 752, the contact element 753 of the relay 722 and a conductor 756 to the other terminal of the contact element 183. The contact element 103, which is actuated at a frequency proportional to the quantity measured at the remote station and to be indicated at the control station will thus continuously make and break the control circuit of the oscillator and cause the oscillator to transmit impulses to the control station at a frequency proportional to the metered quantity to be indicated at the control station.

The operation of the point relay 310 also closes an energizing circuit for the pendulum relay 1 l 8 at the remote station which extends from positive potential through the contact element H4 of the receiving relay H2 in released position, a conductor "158, the winding of the relay H8, a conductor 16!], and a contact element 162 of the point relay 3H1 to negative potential. The pendulum relay I I 8 will thus be intermittently energized and deenergized in accordance with the frequency of the telemetering impulses.

When the coded impulses initiated at the remote station by the operation of the point relay 3H] and transmitted to the control station over the transmission line are received at the control station, the receiving relay l2 will be actuated in accordance with these coded impulses and will intermittently energize the receiving relay 200 at the control station in a circuit which extends from positive potential through the contact element 5M of the relay 5l2, a conductor 528, the winding of the relay 200, a conductor 53% and a contact element 532 of the point relay I34 in released position to negative potential. This coded pulsing of the relay 200 will cause the supervisory control apparatus at the control station to select and operate the point relay l34 which will close its own holding circuit comprising its contact element I68 and the contact element 232 of the relay 2| l in operating position as explained in the Boswau patent.

The operation of the point relay 134 will connect the impulse receiver at the control station to be energized by the receiving relay 512 in a circuit which extends from positive potential through the contact element 5H1 of the relay 5 [2, the conductors 528 and 534, the contact element 5H5 of the point relay I34 and a conductor 53in through the impulse receiver to negative potential. The operation of the point relay I34 will cause its contact element 532 to move to open circuit position to thus remove negative return potential from the relay 200 to prevent it from being pulsed by the telemetering impulses received by the receiving relay H2. The system will thus function to transmit telemetering impulses from the remote station at a frequency proportional to the metered quantity at the station, the impulses will be received at the control station, and the impulse receiver at the control station will be actuated in accordance with the frequency of the telemetering impulses. The indicator at the'control station which is connected to be actuated by the impulse receiver will indicate at the control station the measured quantity at the remote station.

The pendulum relay 5 l 8 at the control station is normally held energized in a circuit which extends from positive potential through a contact element 538 of the relay 529 in released position, a conductor 54D and the winding of the pendulum relay 5l8 to negative potential.

When it is desired to disconnect the telemetering apparatus associated with point No. a at the two stations and restore the supervisory control apparatus to normal, the operator at the control station will operate the telemetering reset key 522 to close an energizing circuit for the relay 520 at the control station extending from positive potential through the reset key 522, a conductor 542, a contact element 544, of the point relay 134, conductors 546 and 548, the contact elements MS of the pendulum relay Bill, a conductor 550 and the winding of the relay 520 to negative potential. This energization of the relay 520 will cause it to move its contact element 538 to actuated position to thus deenergize the pendulum relay 518,. The actuation of therelay 520 will cause it to close its own holding circuit which extends from positive potential through the contact element 552 of the relay 520, a conductor 548, contact elements 5H3 of the pendulum relay 5H3. a conductor 55!), and the winding of the relay 520 to negative potential. The relay 520 will thus be held actuated for the period required for the oscillating contact elements 5|9 of the pendulum relay 5! 8 to cease oscillating and to thereby break the holding circuit of the relay 520. The actuation of the relay 52!] will complete an energizing circuit for the pulsing relay 21]! which extends from positive potential through the contact element 538 in operated position, a conductor 554 and the winding of the relay 20! to negative potential. The relay 20! will thus close its contact element 5H) to cause a long impulse to be transmitted to the remote station. The actuation of the relay 520 will also close a connection to negative potential for the line relay 200 which extends from positive potential through the contact element 5M of the relay 512 which will be energized by the long pulse caused by the energization of the relay 21H, the conductor 528, the winding of the relay 290, the conductor 530, a conductor 55:: and a contact element 558 of the relay 525 to negative potential.

The ions impulse applied to the line relay 200 will cause it to actuate its contact element 221 to break the circuit of the reset relay 202 which will permit its armature 228 to be released to break the indirect positive connection of the supervisory control system at the control station to thus reset the supervisory control apparatus and return the control apparatus to normal. The breaking of the connection to indirect positive will interrupt the holding circuit of the point relay 134 which, as described hereinbefore, includes the contact element 232 of the relay 2! I. At the end of the interval of oscillation of the contact element 519 of the relay pendulum 5l8, the contact elements of the relay 528 will be released and an energizing circuit will again be established for the pendulum relay 5H8 by the contact element 538 of the relay 529 in released position.

When the long release impulse is received at the remote station, receiving relay H2 will be energized for the interval of this release impulse, thus breaking the circuit of the pendulum relay H3 by the movement of the contact element H4 of the relay NZ to operated position. After an interval determined by the period of oscillation of the contact elements H9 of the pendulum relay H8, the relay 720 will release to close an errergizing circuit for the line relay 400 which extends from positive potential through the contact element H 3 of the relay H2, the conductor 129, the winding of the relay 409, the conductors 13D and 132, the contact element 128 of the relay 723, a conductor I64 and the contact element 134 of the relay 722 in actuated position, to negative potential. The release impulse will be so timed as to be suihciently long as to cause the receiving relay "H2 to maintain the relay 40!) energized until the reset relay 402 whose circuit is broken by the actuation of the contact element 428 of the relay 4% to release its contact element 42! to thus reset the supervisory control apparatus at i the remote station by removing the indirect positive connection as fully described in the hereinbefore referred to Boswau patent.

The point relay 310 at the remote station will be released by the disconnection of the indirect positive connection which formed a part of its holding circuit through the contact element 431 or the relay 4 I 2. The deenergization of the point relay 3H5 will permit its contact element 716 to break the energizing circuit for the oscillator which was controlled by the contact element 703 of the telemetering transmitter. The contact element 762 of the point relay 310 will interrupt the energizing circuit for the pendulum relay H8 so that it will not be again energized when the contact element H4 of the relay 1 l 2 is released at the end of the release impulse. The release of the contact element 143 of the point relay 3H] will interrupt the energizing circuit of the relay I22 and permit its contact element 734 to again restore negative return potential to the line relay 400.

After these operations, the supervisory control apparatus at both stations will be in normal po sition ready to be utilized for point selection and operation over other supervisory control points or telemetering over any other control point with which similar telemetering apparatus may be associated.

It is to be understood that the pendulum relays 5|8 and H8 are merely illustrative of one type of relay by which a considerable time delay release may be provided and that any equivalent time delay relay may be used to perform the function of these pendulum relays. It is also to be understood that the telemetering transmitter at the remote station may be any suitable means for operating the contact element 103 at a frequency proportional to the quantity at the remote station which is to be indicated at the control station, and that the impulse receiver at the control station may be any suitable device which will respond to and be actuated in accordance with the frequency of impulses applied thereto. It is to be further understood that the carrier current apparatus illustrated and described herein is merely illustrative of the form which this apparatus may take, and that this apparatus may be any apparatus which will transmit impulses between two stations whether or not there be a direct conductor connection between the stations.

Thus it will be seen that I have provided a combined supervisory control and impulse type remote metering system whicheshaiLi-unction to perform impulse selection control and supervisiory operations and impulse type telemetering operations between two stations employing but a single communication channel.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my inven tion. It is to be understood, however, that the invention is not limited to the precise construction herein disclosed, but is capable of modification by one skilled in the art, the embodiments herein disclosed being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a combined supervisory control and remote metering system, a carrier current channel extending between a control station and a remote station, supervisory control means at the stations, means including said superviosry control means for selectively operating from the control station over the carrier current channel a plurality of point relays at the remote station, means including said supervisory control means responsive to the operation of a selected point relay at the remote station for operating a corresponding point relay at the control station, an impulse device at the remote station operable at a frequency proportional to a quantity to be indicated at the control station for transmitting telemetering impulses from the remote to the control station over said carrier current channel at frequencies proportional to the said quantity, mean s responsive to the operation of said selected point relay at the remote station for connectin said impulsedevice at the remote station in transmitting relation, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the supervisory control means of longer duration than any of the quantity indicating impulses, and means responsive to the application of such a release impulse only to the supervisory control means for deenergizing said operated point relays at the control and remote stations.

2. In a combined supervisory control and remote metering system, a carrier current channel extending between a control station and a remote station, supervisory control means at the stations operable in response to selective coded impulses, means including said supervisory control means for selectively operating by coded impulses sent from the control station over the carrier current channel a plurality of point relays at the remote station, means including said supervisory control means responsive to the operation of one of said point relays at the remote station for operating a corresponding point relay at the control station, an impulse device at the remote station operable in accordance with a quantity to be indicated at the control station for transmitting telemetering impulses from the remote to the control station over said carrier current channel at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device at the remote station in impulse transmitting relation, frequency responsive means at the control station 'esponsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for conneoting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the supervisory control means of longer duration than any of the quantity indicating impulses, and means responsive to the application of such a release impulse only to the supervisory control means for deenergizing said operated point relays at the control and remote stations.

3. In a combined control and remote metering system, a communication system connecting a control and a remote station, control means at the stations operable in response to selective coded impulses, means including said control means for selectively operating by coded impulses sent from the control station over said communication system a plurality of point relays at the remote station, means including said control means responsive to the operation of one of said point relays at the remote station for operating a corresponding point relay at the control sta-' tion, an impulse device at the remote station operable in accordance with a quantity to be indicated at the control station for transmitting telemetering impulses from the remote to the control station over said communication system at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device at the remote station in impulse transmitting relation with said communication system, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the said control means of longer duration than any of the quantity indicating impulses, and

means responsive to the application of such a release impulse only to the said control means for deenergizing said operated point relays at the control and remote stations.

4. In a combined control and remote metering system, a communication system connecting a control and a remote station, control means at the stations operable in response to selective coded impulses, means including said control means for selectively operating by coded impulses sent from the control station over said communication system a plurality of point relays at the remote station, means including said control means responsive to the operation of one of said point relays at the remote station for operating a corresponding point relay at the control station, means responsive to the operation of the means for operating said corresponding point relay at the control station for rendering said control means at the remote station unresponsive to impulses on the communication system, Jeans responsive to the operation of the said corresponding point relay at the control station for rendering the said control means at the control station unresponsive to impulses on the communication system, an impulse device at the remote station operable in accordance with a quantity to be indicated at the control station for transmitting telemeteringimpulses from the remote to the control station over said communication system at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device in impulse transmitting relation with the communication system, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, and means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station.

5. In a combined control and remote metering system, a communication system connecting a control and a remote station, control means at the stations operable in response to selective coded impulses, means including said control means for selectively operating by coded impulses sent from the control station over said communication system a plurality of point relays at the remote station, means including said control means responsive to the operation of one of said point relays at the remote station for operating a corresponding point relay at the control station, means responsive to, the operation of the means for operating said corresponding point relay at the control station for rendering said control means at the remote station unresponsive to impulses on the communication system, means responsive to the operation of the said corresponding point relay at the control station for rendering the said control means at the control station unresponsive to impulses on the communication system, an impulse device at the remote station operable in accordance with a quantity to be indicated at the control station for transmitting telemetering impulses from the remote to the control station over said communication system at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device in impulse transmitting relation with the communication system, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the communication system of longer duration than any of the quantity indicating impulses, and means responsive to the application of such a release impulse only to the communication system for deenergizing said point relays and restoring said control means to impulse responsive condition.

6. In a combined remote control and remote metering system, a communication system connecting a control and a remote station, an impulse means at the remote station for transmitting impulses over the communication system at frequencies proportional to a quantity to be indicated at the control station, means operable over said communication system from the control station for connecting said impulse means in impulse transmitting relation with said communication system, an impulse responsive means at the control station, means for connecting said impulse responsive means in impulse receiving relation with said communication system, means for applying a release impulse to the communication system of longer duration than any of the quantity indicating impulses, and means responsive only to such a release impulse on said communication system for disconnecting said impulse transmitting and receiving means from transmitting and receiving relation with the communication system.

7. In a combined control and remote metering system, a communication system connecting a control and a remote station, control means at the stations operable in response to selective coded impulses, means including said control means for selectively operating by coded impulses sent from the control station over said communication system a plurality of point relays at the remote station, means including said control means responsive to the operation of one of said point relays at the remote station for operating a corresponding point relay at the control station, an impulse device at the remote station operable in accordance with a quantity to be in dicated at the control station for transmitting telemetering impulses from the remote to the control station over said communication system at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device at the remote station in impulse transmitting relation with said communication system, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the control means of longer duration than any of the quantity indicating impulses, and means responsive to the application of such a release impulse only to the said control means for deenergizing said operated point relays at the control and remote stations, said means respon-- sive to a release impulse comprising reset means at the control and remote stations for deenergizing said operated point relays at the control and remote stations.

8. In a combined control and remote metering system, a communication system connecting a control and a remote station, control means at the stations operable in response to selective coded.-irnpulses,wmeansnincludingr. said. control.

dicated at the control station 'ior tfansmitting telemetering impulses from the remote to the control station over said communication system at frequencies proportional to the said quantity, means responsive to the operation of said one selected point relay at the remote station for connecting said impulse device at the remote station in impulse transmitting relation with said communication system, frequency responsive means at the control station responsive to the frequency of the impulses transmitted from the remote station, means responsive to the operation of the said corresponding point relay at the control station for connecting said frequency responsive means to be actuated by the impulses transmitted from the remote station, means at the control station for applying a release impulse to the control means of longer duration than any of the quantity indicating impulses, and means responsive to the application of such a release impulse only to the said control means for deenergizing said operated point relays at the control and remote stations, said release impulse applying means comprising a first relay and a second relay, said first relay being normally energized, means for momentarily energizing said second relay, means whereby energization of said second relay deenergizes said first relay, means whereby the deenergization of said first relay causes said second relay to be energized for a predetermined length of time, and means whereby said second relay causes an impulse to be applied to the control means for the duration of the energization of the second relay.

WILLARD A. DERR. 

